This invention relates to masonry wall and building construction and more particularly relates to an improved prefabricated footing system and an improved concrete masonry footing block.
The footings for masonry structures and particularly for masonry housing are conventionally prepared by digging trenches in accordance with the layout of the house, forming frameworks for the footing in the trenches and pouring concrete in the space formed by the framing so as to form a continuous footing. Relatively recently prefabricated concrete footing blocks have been utilized. Foundations formed in this manner generally involve the placement in the foundation trenches of the required number of precast footing blocks which are leveled and supported directly on the ground or by means of a sub-base or substrate of gravel or any other suitable material. The prefabricated footing blocks which have been proposed heretofore have generally been of an elongated shape and these have been disposed horizontally in an end-to-end fashion along their major axes to serve as a footing for masonry wall mounted thereon with the major axes of the footing blocks extending in the same direction as the longitudinal axes of the wall.
Blocks of this general type are illustrated by way of example in Canadian Patent No. 1,077,281 issued May 13, 1980. These particular blocks are formed of precast concrete with an inverted T cross section and are provided with a plurality of bores in the widened base to permit the pouring of concrete or mortar to minimize the difficulties which had previously been encountered in laying a uniform and adequately anchored footing of prefabricated blocks. Another example of prefabricated footing or foundation blocks is illustrated in U.S. Pat. No. 894,122 issued July 21, 1908. The blocks shown in that patent are of a curved elongated form and show a masonry construction for a circular grain bin.
Probably the most analogous prior commercial prefabricated footing blocks are the "Leca Foundation Block" made by A/S Norsk Leca of Norway. The Leca system is based on a concrete masonry footing block unit which is 20 inches (50 cm) long, 12 inches (33 cm) wide and 6 inches (17 cm) thick. The Leca footing blocks are installed with the block's longest axis extending in the direction of the wall, and the blocks are interlocked at their ends without mortar.
While prefabricated footings of these prior types provide certain advantages over poured concrete footings, they have thus far also presented certain problems and disadvantages. The prefabricated blocks are generally relatively heavy (over 50 pounds, for example) and present certain difficulties in transportation and handling. The weight of the blocks and the type of handling which is necessitated tends to cause the workmen to tire and can result in higher costs and/or flawed footings and surmounting walls due to imprecise placement of the blocks as the workers tire. Further, the maximum weight of block that may be readily handled manually by workmen imposes a practical limit on the width of the footing and therefore its utility for use in poor soil conditions. A still further disadvantage in the known prefabricated footing blocks proposed to date is their limitation to use with walls of predetermined types and dimensions and their lack of adaptation to the varied foundations and wall structures generally found to be desirable in building construction.